Microstrip Antenna, Wireless Tag Communication Device, and Sheet Processing Device

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2024-060593, filed on Apr. 4, 2024, the entire contents of which are incorporated herein by reference.

Embodiments described herein relate generally to a microstrip antenna, a wireless tag communication device, and a sheet processing device.

An image forming device may form an image on a sheet provided with a wireless tag such as a radio frequency identifier tag (RFID). Such an image forming device may exchange information with the wireless tag on the sheet via radio waves using a microstrip antenna provided with multiple types of radiating elements capable of transmitting and receiving radio waves. However, the efficiency of energy conversion from electrical signals to radio waves by microstrip antennas was not always good.

The problem to be solved by the present disclosure is to provide a microstrip antenna, a wireless tag communication device, and a sheet processing device that can improve the efficiency of energy conversion from an electrical signal to radio waves.

In general, according to an embodiment, a microstrip antenna includes a radiating element. The radiating element includes a first radiation area including a first major axis which is a major axis parallel to a first direction and a first minor axis which is a minor axis perpendicular to the first major axis, and a second radiation area including a second major axis which is a major axis parallel to the first direction and longer than the first major axis and a second minor axis which is a minor axis perpendicular to the second major axis. A length of the second minor axis is shorter than a length of the first minor axis.

Hereinafter, a wireless tag communication device and a sheet processing device according to the embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are designated by the same reference numerals. In addition, description of duplicated configurations may be omitted.

is a diagram illustrating an example of an image forming deviceaccording to an embodiment. The image forming deviceis an example of a sheet processing device.

In, the image forming deviceincludes a control panel, a wireless tag communication device, and a printer unit. The printer unitincludes a control unit, paper feeding cassettesand, and the like. The control unit(e.g., controller) controls the control panel, the wireless tag communication device, and the printer unit. The control unitcontrols the conveyance of the sheet in the printer unit. As used herein “controlling sheet conveyance” and like terms means controlling the timing of sheet conveyance, a stop position of the sheet, a conveyance speed of the sheet, and the like.

The control panelincludes an input key and a display unit. For example, the input key receives input by a user. For example, the display unit is a touch panel type unit (e.g., a touch sensitive display). The display unit receives input from the user and displays the input to the user. For example, the control paneldisplays items related to the operation of the image forming deviceon the display unit in a configurable manner. The control panelnotifies the control unitof the items set/selected by the user.

The paper feeding cassettesandstore sheets on which wireless tags are provided. Of course, the paper feeding cassettesandcan also store sheets not provided with wireless tags. In the following description, unless otherwise specified, the sheet is a sheet provided with a wireless tag. The sheet is made of a material such as paper or plastic film.

The printer unitperforms image formation operations. For example, the printer unitforms an image represented by image data on a sheet. In the following description, forming an image on the sheet is also referred to as printing. The printer unitincludes an intermediate transfer belt. The printer unitsupports the intermediate transfer beltwith a driven roller, a backup roller, and the like. The printer unitrotates the intermediate transfer beltin the direction of an arrow m.

The printer unitincludes four sets of image forming stations,,, and. The image forming stations,,, andare for forming images of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The image forming stations,,, andare disposed below the intermediate transfer beltalong a direction of rotation of the intermediate transfer belt.

Hereinafter, the image forming stationfor Y (yellow) among the image forming stations,,, andwill be described as an example. Since the image forming stations,, andhave the same configuration as the image forming station, detailed description thereof will be omitted.

The image forming stationincludes an electrostatic charger, an exposure scanning head, a developing device, and a photoconductor cleaner. The electrostatic charger, the exposure scanning head, the developing device, and the photoconductor cleanerare arranged around a photoconductor drumrotating in the direction of an arrow n.

The image forming stationincludes primary transfer rollers. The primary transfer rollersface the photoconductor drumwith the intermediate transfer beltinterposed therebetween.

The image forming stationcharges the photoconductor drumwith the electrostatic chargerand then exposes the drum to light with the exposure scanning head. The image forming stationforms an electrostatic latent image on the photoconductor drum. The developing devicedevelops the electrostatic latent image on the photoconductor drumusing a two-component developer made of toner and carrier.

The primary transfer rollersperform primary transfer of the toner image formed on the photoconductor drumonto the intermediate transfer belt. The image forming stations,,, andform a color toner image on the intermediate transfer beltby the primary transfer rollers. The color toner image is formed by sequentially overlapping toner images of Y (yellow), M (magenta), C (cyan) and K (black). The photoconductor cleanerremoves the toner remaining on the photoconductor drumafter the primary transfer.

The printer unitincludes secondary transfer rollers. The secondary transfer rollersface the backup rollerwith the intermediate transfer beltinterposed therebetween. The secondary transfer rollerssecondarily transfer the color toner images on the intermediate transfer beltto the sheet all at once. In the following description, the term “toner image” may refer to either a color toner image or a toner image of only one color. The toner image may be a toner image using a decolorizing toner.

A conveyance pathis a conveyance path from a junctionto a branch portion. A conveyance pathis a conveyance path that passes through a double-sided printing deviceand is a conveyance path from the branch portionto the junction. A conveyance pathis a conveyance path from the branch portionto a discharge tray.

A tip end of a sheet picked up from the paper feeding cassette, the paper feeding cassette, or a manual feed trayis abutted against a portion where the two registration rollersare in contact with each other while the two rollers are stopped. The sheet that is struck against the registration rollerhas its inclination corrected. The control unitstarts the rotation of the registration rollersin accordance with a position of the toner image on the rotating intermediate transfer beltand moves the sheet to a position of the secondary transfer rollers. The control unitcontrols the secondary transfer rollersto secondarily transfer the toner image formed on the intermediate transfer beltonto the sheet. The control unitconveys the sheet to the conveyance pathand forms an image by fixing the toner image on the sheet by a fixing device. The control unitconveys the sheet on which the image is formed to the conveyance path, and then discharges the sheet.

In a case of double-sided printing, the control unitconveys the sheet on which an image is formed on the front side to the conveyance path. After the entire sheet passes through the branch portion, the control unitswitches back and conveys the sheet to the conveyance path. Thereafter, the control unitconveys the sheet to the junctionvia the conveyance path in the double-sided printing deviceand conveys the sheet to the conveyance pathvia the registration rollers. The control unitthen fixes the toner image by the fixing deviceto form an image on the back side of the sheet. The control unitconveys the sheet having the image formed on the back side to the conveyance path, and then discharges the sheet.

The wireless tag communication deviceis capable of communicating with the control unit(e.g., communicatively coupled with the control unit). The wireless tag communication devicecommunicates with the wireless tag of the sheet to read information from the wireless tag and write information to the wireless tag. The wireless tag communication devicetransmits a signal in a direction of an arrow k. The signal is specifically a modulated radio wave. Information is written to the wireless tag of the sheet by the signal transmitted from the wireless tag communication device.

The image to be formed in the printer unitis formed on the photoconductor drumas an electrostatic latent image from the exposure scanning headbefore being secondarily transferred to the secondary transfer rollers. The electrostatic latent image formed on the photoconductor drumis primarily transferred to the intermediate transfer beltas a toner image. Furthermore, the toner image primarily transferred onto the intermediate transfer beltis secondarily transferred onto the wireless tag sheet conveyed to the position of the registration rollers.

Next, a functional block diagram of the image forming device according to the embodiment will be described with reference to. In, the image forming deviceincludes the control unit, the control panel, the printer unit, and the wireless tag communication device.

The control unitincludes a calculation device(e.g., a processor, processing unit, etc.) and a storage device(e.g., memory, memory device, etc.). The calculation devicecontrols the control panel, the printer unit, and the wireless tag communication deviceaccording to an image processing program stored in the storage device. The control unitoutputs, for example, information indicating that the conveyance of the sheet is started (hereinafter, referred to as “conveyance start information”).

The calculation deviceis, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), or the like. The storage deviceis a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a solid state drive (SSD), or the like. A data reception unit(e.g., a communication interface) receives print data (for example, data written in a page description language) indicating an image to be printed from a host such as a personal computer (PC) and stores the received print data in the storage device. An image data developing unitdetermines printing conditions from the print data stored in the storage deviceby the data reception unit, and develops the data into printable data (e.g., raster data) for the printer unitto store in the storage device.

The printer unitincludes the fixing device, the secondary transfer rollers, and the developing device. The printer unitforms an image on a sheet based on the data stored in the storage deviceby the image data developing unit.

is a diagram illustrating an example of a position where a sheet is capable of being present in the image forming deviceof the embodiment. In, a sheet Sb indicates a sheet placed on the paper feeding cassette. A sheet Sc indicates a sheet placed on the discharge tray. A sheet Sd indicates a sheet placed on the manual feed tray. The paper feeding cassettesand, the discharge tray, and the manual feed trayare examples of a placement unit.

A sheet Sa indicates a sheet being conveyed along the conveyance path. Each sheet is provided with a wireless tag.

In, the sheet on which information is to be written to the wireless tag (hereinafter, also referred to as the “target sheet”) is a sheet being conveyed along the conveyance path. Therefore, the sheet Sa is an example of a target sheet.

In the state illustrated in, the wireless tag communication devicetransmits a signal in the direction of the arrow k. That is, the k direction is the transmission direction of the signal transmitted by the wireless tag communication device. Therefore, the k direction is also a propagation direction of the radio waves emitted by the wireless tag communication device.

Each wireless tag that receives a signal performs an action according to the content of the received signal. The wireless tag stores information indicated by the received signal, for example. The wireless tag responds to, for example, the wireless tag communication device. Responding specifically means sending a signal. The wireless tag communication devicereceives a signal transmitted from the wireless tag provided on each sheet. In the case of, one of the wireless tags that receives the signal is the wireless tag provided on the sheet Sa. In, the sheet Sa is being conveyed.

The wireless tag has a shape having a major axis and a minor axis in a plane perpendicular to the k direction, and when the wavelength of the radio wave is the same, the wireless tag interacts more strongly with a polarized wave whose polarization plane is parallel to the major axis than with a polarized wave whose polarization plane is perpendicular to the major axis. Strong interaction means that there is a low probability that the radio waves will penetrate the wireless tag, and there is a high probability that the radio waves that reach the wireless tag will be absorbed or reflected by the wireless tag. Therefore, it is preferable for the wireless tag communication deviceto use radio waves whose polarization plane is parallel to the major axis of the wireless tag in order to exchange information with the wireless tag, from the viewpoint of power consumption and low frequency of communication errors. The occurrence of the communication errors means that information cannot be exchanged between the wireless tag communication deviceand the wireless tag.

is a diagram illustrating an example of the relationship between the arrangement of wireless tags on a sheet and the conveyance direction of the sheet in the embodiment. In, tags Ta, Tb, Tc, and Td are examples of wireless tags provided on the sheet Sa being conveyed through the conveyance path. The tag Ta is an example of a wireless tag that is provided on the sheet Sa so that the major axis is perpendicular to the conveyance direction and perpendicular to the major axis direction of the sheet surface. The tag Tb is an example of the wireless tag that is provided on the sheet Sa such that the major axis is parallel to the conveyance direction and parallel to the major axis of the sheet Sa. The tag Tc is an example of the wireless tag that is provided on the sheet Sa such that the major axis is perpendicular to the conveyance direction and parallel to the major axis of the sheet Sa. The tag Td is an example of the wireless tag that is provided on the sheet Sa such that the major axis is parallel to the conveyance direction and perpendicular to the major axis of the sheet Sa. Althoughillustrates an example in which one wireless tag is disposed on one sheet, it is not necessary to dispose only one wireless tag on one sheet, and multiple wireless tags may be disposed on one sheet.

The conveyance direction of the sheet is, for example, a direction perpendicular to the k direction inand is a direction from bottom to top on the sheet surface of. In addition, since the wireless tag is attached to the sheet, the conveyance direction of the sheet is also the conveyance direction of the wireless tag.

is a diagram illustrating an example of the configuration of the wireless tag communication deviceaccording to the embodiment. The wireless tag communication deviceincludes an antenna, a wireless tag communication control unit, a transmitting and receiving circuit unit, and an interface unit.

The antennatransmits a signal. The antennareceives an incoming signal. A carrier of the signal transmitted by the antennais radio waves. A carrier of the signal received by the antennais radio waves.

The wireless tag communication control unitis configured using a processorsuch as a CPU and a memory. The wireless tag communication control unitoperates by the processorreading a program stored in the memoryand executing the read program. The wireless tag communication control unitcontrols the operation of each functional unit included in the wireless tag communication device. A write threshold is stored in advance in the memory.

The wireless tag communication control unitreceives, for example, the sheet conveyance start information. The wireless tag communication control unitcontrols the operation of each functional unit included in the wireless tag communication deviceto cause the wireless tag communication deviceto transmit a signal. The wireless tag communication control unitdemodulates a signal received by the antennaby controlling the operation of each functional unit included in the wireless tag communication device, for example. The wireless tag communication control unitmeasures the elapsed time after receiving the conveyance start information, for example.

The transmitting and receiving circuit unitincludes a modulation unit, a transmission amplifier, a reception amplifier, a demodulation unit, a circulator, and a changeover switch.

The modulation unitmodulates the radio waves emitted by the wireless tag communication device. More specifically, a voltage modulated by the control of the wireless tag communication control unitis applied to the modulation unit, and the application of the voltage causes the modulation unitto generate a modulated current. The current generated by the modulation unitflows through the transmission amplifier, and then the antennagenerates radio waves. The radio waves generated by the antennaare the radio waves emitted by the wireless tag communication device. In this way, the radio waves modulated by the modulation unitis the radio waves emitted from the antenna, and therefore, the radio waves modulated by the modulation unitis the signal transmitted by the wireless tag communication device.

The transmission amplifiercontrols the strength of the signal transmitted by the wireless tag communication device. The circulatorseparates the signal transmitted by the antennafrom the signal received by the antenna.

The changeover switchswitches the application destination of the voltage (that is, the target to which the current modulated by the modulation unitand amplified by the transmission amplifierflows). Specifically, the changeover switchswitches the connection destination of the transmission amplifierto one of feedersanddescribed later. The changeover switchis, for example, a radio frequency (RF) switch such as a single-pole double-throw switch. The operation of the changeover switchis controlled by the wireless tag communication control unit. The changeover switchis operated under the control of the wireless tag communication control unit, and the voltage application destination is switched.

The reception amplifiercontrols the strength of the signal received by the antennato a predetermined strength. The demodulation unitdemodulates the signal received by the antenna.

The interface unitis an interface that electrically connects the wireless tag communication control unitand the control unit.

is a diagram illustrating an example of a side view of a configuration of the antennaaccording to the embodiment. The antennais a microstrip antenna including a ground conductor plate, a dielectric substrate, and a radiating element. The ground conductor plateis a ground conductor. The dielectric substrateis a dielectric material that is in contact with the ground conductor plate.

The radiating elementis a conductor located on the side opposite to the ground conductor platewith the dielectric substrateinterposed therebetween and is a conductor in contact with the dielectric substrate. The radiating elementis connected to the feedersandthat pass through the dielectric substrateand the ground conductor plate. The feedersandare conductors. When a voltage is applied to the radiating elementvia either the feederor, the radiating elementemits radio waves generated by the current generated by the applied voltage. The emitted radio waves are the signal. The wave vector of the radio waves emitted by the radiating elementis a vector pointing in the k direction. Hereinafter, when there is no distinction between the feederand the feeder, it will be referred to as a feeder. The end of the feederthat is not in contact with the radiating elementis connected to the changeover switch.

For the sake of simplicity, a plane perpendicular to the k direction is referred to as an XY plane. Hereinafter, of the two mutually orthogonal vectors that span the XY plane, the vector perpendicular to the conveyance direction of the sheet conveyed on the conveyance pathis referred to as an X vector, and the vector perpendicular to the X vector is referred to as a Y vector.

The shape of the surface of the radiating elementperpendicular to the k direction is substantially the same regardless of the position in the k direction. The length of the radiating elementin the k direction is preferably shorter than the wavelength of the radio waves emitted by the radiating element, and particularly preferably a length less than ¼ of the wavelength.

is an explanatory diagram illustrating an example of a shape of the radiating elementin the XY plane (hereinafter, referred to as the “radiating element shape”) in the embodiment. The direction perpendicular to the sheet surface ofis parallel to the k direction.